1. Field of the Invention
This invention relates to a process for concentrating fruit or vegetable juices wherein losses of flavor and color components, which ordinarily occur during concentration processes, is substantially avoided. More particularly, the invention relates to an efficient system for separating and recovering flavor and color components from citrus juices in connection with concentration processes.
2. Description of Related Art
It has been known to concentrate fruit and vegetable juices by evaporating water from the juice. Evaporation is perhaps the simplest, quickest and least expensive way to concentrate juice. However, evaporation processes involve heating the beverage under conditions which sometimes promote hydrolysis and/or oxidation of components of the beverage. This can cause chemical alterations of the aroma and flavor compounds. Such degradation of the flavor components can cause off flavors in the concentrated beverage. Thus, conventional evaporation processes can result in off-flavors and flavor loss in the juice product produced.
Numerous methods have been devised to compensate for the loss of aroma and flavor during evaporation concentration processes.
For example, U.S. Pat. No. 3,248,233 to Brent et al. discloses a method of minimizing the overall loss of aroma and flavor compounds by collecting "essence" of the juice. Essence is the term usually applied to the first 15% to 20% of the water which is removed through evaporation and which contains a significant amount of volatile aroma and flavor compounds. The escaping essence is condensed, the aroma and flavor compounds recovered and rectified as water is removed, and then added back to concentrated juice.
These types of procedures are not totally satisfactory because not all of the escaping aroma and flavor volatile compounds are usually collected and recovered. See U.S. Pat. No. 4,971,811. Thus, there can be a significant loss in the overall aroma and flavor of the final concentrated product.
Different procedures for adding back certain volatile compounds and essences to concentrated beverages to enhance the overall flavor of the juice have been proposed. However, it is generally recognized that while such modified evaporation concentration processes are useful and fairly effective, there may still be a significant loss of aroma and flavor compounds which occur.
Freeze concentration equipment provides an alterative to the use of evaporators. In freeze concentration the objective is to remove water in the form of ice crystals without removing significant amounts of aroma and flavor volatiles. Ideally, in freeze concentration only pure ice should be removed without removing any of the aroma and flavor compounds present in the original juice. If the recovered ice contains occluded aroma and flavor compounds, a somewhat inferior quality juice concentrate is usually produced.
However, studies have shown that significant amounts of aroma and flavor compounds can also be lost during freeze concentration as well. See U.S. Pat. No. 4,463,025. Average loss of aroma and flavor compounds in the ice during each successive concentration was estimated to be around 12%. It is possible also that a loss of overall quality occurred because a number of oxidation products were formed during this freeze concentration process, such as nootkatone, carvone, geraniol, and alphaterpineol. See U.S. Pat. No. 4,463,025. The formation of these oxidation products and similar compounds will usually result in a juice product having a notable off-flavor.
Accordingly, attempts have been made to remove the flavor and aroma components from juice to result in a serum which can subsequently be subjected to freeze concentration. The separated flavor components are returned to the serum after freeze concentration. See U.S. Pat. Nos. 4,463,025 and 4,569,853. However, these processes have relied upon centrifugation and/or ultra-filtration to separate the flavor components from the juice.
There are certain drawbacks to the use of centrifuges and filters. Very high pressures are required to maintain the flow of juice through the membranes or screens used for filtration. Even when using very high pressures, the filters sometimes have a tendency to become clogged so that the process must be frequently interrupted to clean or replace them.
Another disadvantage is that centrifugation and filtration require expensive equipment and special carefully controlled conditions. For example, it is important that the centrifugation be conducted in the absence of oxygen. See U.S. Pat. No. 4,569,853. This requires that the centrifuge be hermetically sealed in an inert gas such as nitrogen.
It is an object of the present invention to provide a system for separating substantially all of the flavor components out of a juice to be concentrated which does not require centrifugation or high pressure filtration.
It is a further object of the invention to provide a system capable of removing substantially all of the flavor components from a juice without any substantial susceptibility to microbial contamination.
It is yet a further object of the invention to provide a process for concentrating citrus juice by evaporation without any significant loss or oxidation of the flavor and aroma components.